Bioenergy, Solar

IMEC builds a better Ge-based TPV

At its annual Technology Forum in Belgium, IMEC says it has devices a better way to make germanium-based thermophotovoltaic (TPV) cells, fabricated on substrates “with an optimized surface,” that significantly reduces their cell costs.

June 10, 2010 – IMEC says it has devices a better way to make germanium-based thermophotovoltaic (TPV) cells, fabricated on substrates “with an optimized surface,” that significantly reduces their cell costs.

TPV cells, which convert radiation from heat sources (temperatures lower than the sun’s temperature), are generally best suited for industrial uses, e.g. generating electricity from waste heat released from steel or glass production. They can also be incorporated into domestic heating systems to cogenerate electricity besides hot water, and thus can reduce waste (and increase efficiency) of domestic heating systems. But due to complexity of full TPV systems and relatively high cost of existing suitable cells, TPV systems haven’t gained traction in either industrial or consumer use.

 

 

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IMEC’s germanium-based thermophotovoltaic cell with an optimized front and rear surface finishing. (Source: IMEC)


Enter IMEC and its new fabrication process, which leverages the group’s work in surface passivation techniques, novel contacting technologies, and materials knowledge. Germanium-based TPV cells — well-suited as receivers due to their bandgaps, which are relatively close to the emission peaks of TPV selective emitters — are typically fabricated on epi-ready substrates originally made for epitaxial growth of III-V layers. But IMEC’s new method uses no epi deposition steps — the emitter is formed by diffusion and passivation, through use of amorphous Si.

Specifically designed Ge substrates have been manufactured and tested, with spectral response measurements showing TPV cells on specifically engineered Ge substrates possess “remarkably better quantum efficiency” than traditional TPV cells with epi-ready substrates, IMEC notes — and this translates into higher waste heat to electric conversion efficiency.

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TPV cells on specially engineered substrates show improved performance at wavelengths relevant for thermophotovoltaic applications. (Source: IMEC)